| 摘要 |
PROBLEM TO BE SOLVED: To prevent a seam from fraying from the end of the seam in forming a double-loop seam on a cloth and obtain a sewn product with good appearance by changing the length of the looper thread running out of the end of the seam. SOLUTION: This seam fray preventive device of a sewing machine, which has needles 5 and 6 and a looper 3 oscillating almost horizontally between the forward moving position and the backward moving position with the needles 5 and 6 in-between to form a double-loop seam on a cloth with the needle thread and the looper thread, has a looper thread engaging means 11, a looper thread cutter 12 for cutting loops of the looper thread and a thread cutter 30 for cutting a loop-shaped needle thread and a looper thread. The looper thread engaging means 11 moves to engage with a looper thread and, by driving the sewing machine with the looper thread engaging means engaging with the looper thread, forms loops of the looper thread at the engaging part when the looper 3 is in the forward moving position. The seam fray preventive device also has a control means 27 for controlling the quantity of movement of the looper thread engaging means 11, so that the length of the loops of the looper thread and the length of the thread end cut by the thread cutter 30 and remaining on the cloth can be changed by the control means 27.
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